Augmented Reality (AR) enhances a user's perception of, and interaction with, the real world. Virtual objects are used to display information that the user cannot directly detect with the user's senses. The information conveyed by the virtual objects helps a user perform real-world tasks. Many prototype AR systems have been built in the past, typically taking one of two forms. In one form, they are based on video approaches, wherein the view of the real world is digitized by a video camera and is then composited with computer graphics. In the other form, they are based on an optical approach, wherein the user directly sees the real world through some optics with the graphics optically merged in. An optical approach has the following advantages over a video approach: 1) Simplicity: Optical blending is simpler and cheaper than video blending. Optical see-through Head-Up Displays (HUDs) with narrow field-of-view combiners offer views of the real world that have little distortion. Also, there is only one “stream” of video to worry about: the graphic images. The real world is seen directly through the combiners, which generally have a time delay of a few nanoseconds. Time delay, as discussed herein, means the period between when a change occurs in the actual scene and when the user can view the changed scene. Video blending, on the other hand, must deal with separate video streams for the real and virtual images. Both streams have inherent delays in the tens of milliseconds. 2) Resolution: Video blending limits the resolution of what the user sees, both real and virtual, to the resolution of the display devices, while optical blending does not reduce the resolution of the real world. On the other hand, an optical approach has the following disadvantages with respect to a video approach: 1) Real and virtual view delays are difficult to match. The optical approach offers an almost instantaneous view of the real world, but the view of the virtual is delayed. 2) In optical see-through, the only information the system has about the user's head location comes from the head tracker. Video blending provides another source of information, the digitized image of the real scene. Currently, optical approaches do not have this additional registration strategy available to them. 3) The video approach is easier to match the brightness of real and virtual objects. Ideally, the brightness of the real and virtual objects should be appropriately matched. The human eye can distinguish contrast on the order of about eleven orders of magnitude in terms of brightness. Most display devices cannot come close to this level of contrast.
AR displays with magnified views have been built with video approaches. Examples include U.S. Pat. No. 5,625,765, titled Vision Systems Including Devices And Methods For Combining Images For Extended Magnification Schemes; the FoxTrax Hockey Puck Tracking System, [Cavallaro, Rick. The FoxTrax Hockey Puck Tracking System. IEEE Computer Graphics & Applications 17, 2 (March–April 1997), 6–12.]; and the display of the virtual “first down” marker that has been shown on some football broadcasts.
A need exists in the art for magnified AR views using optical approaches. With such a system, a person could view an optical magnified image with more details than the person could with the naked eye along with a better resolution and quality of image. Binoculars provide much higher quality images than a video camera with a zoom lens. The resolution of video sensing and video display elements is limited, as is the contrast and brightness. One of the most basic problems limiting AR applications is the registration problem. The objects in the real and virtual worlds must be properly aligned with respect to each other, or the illusion that the two worlds coexist will be compromised. The biggest single obstacle to building effective AR systems is the requirement of accurate, long-range sensors and trackers that report the locations of the user and the surrounding objects in the environment. Conceptually, anything not detectable by human senses but detectable by machines might be transduced into something that a user can sense in an AR system. Few trackers currently meet all the needed specifications, and every technology has weaknesses. Without accurate registration, AR will not be accepted in many applications. Registration errors are difficult to adequately control because of the high accuracy requirements and the numerous sources of error. Magnified optical views would require even more sensitive registration. However, registration and sensing errors have been two of the basic problems in building effective magnified optical AR systems.
Therefore, it would be desirable to provide an AR system having magnified optics for 1) generating high quality resolution and improved image quality; 2) providing a wider range of contrast and brightness; and 3) improving measurement precision and providing orientation predicting ability in order to overcome registration problems.
The following references are provided for additional information:    S. You, U. Neumann, & R. Azuma: Hybrid Inertial and Vision Tracking for Augmented Reality Registration. IEEE Virtual Reality '99 Conference (Mar. 13–17, 1999), 260–267.    Azuma, Ronald and Gary Bishop. Improving Static and Dynamic Registration in an Optical See-Through HMD. Proceedings of SIGGRAPH '94 (Orlando, Fla., 24–29 Jul., 1994), Computer Graphics, Annual Conference Series, 1994, 197–204.    Computer Graphics: Principles and Practice (2nd edition). James D. Foley, Andries van Dam, Steven K. Feiner, John F. Hughes. Addison-Wesley, 1990.    Lisa Gottesfeld Brown, A Survey of Image Registration Techniques. ACM Computing Surveys, vol. 24, #4, 1992, pp. 325–376.